This paper describes the epidemiologically relevant events that took place in a dairy herd infected by Salmonella dublin. The evidence presented indicates that it may be possible to eliminate infection from the farm and that residual infection or persistent excretion are uncommon. In two animals infection persisted, in one instance in the tonsil and in the other in the gall bladder. In this latter case the infection remained from the neonatal period until adulthood. It is possible that both these animals are relevant in a more general context and are indicative of the source of infection in outbreaks in which the origin of infection cannot be deter-mined by more routine examinations.

A number of serological tests were evaluated in a study of Salmonella dublin infection in a dairy herd. None of the tests used detected either of the two carrier animals from which Salmonella dublin was isolated at slaughter 7 and 17 months after the herd infection. The complement fixation tests used proved to be a better guide to the presence of recent herd infection than the conventional ‘0’ or ‘H’ agglutination tests.

When a standard sample of a simulated exudate containing known numbers of anaerobic bacteria was taken up on a swab and plated on solid medium, the number of colonies subsequently cultured represented a very small proportion of the original sample. Evidence is produced that the apparent loss is not primarily attributable to inactivation on the swab but rather to retention of organisms on the swab. This was demonstrable with Clostridium welchii and with Bacteroides species that have hitherto been regarded as relatively oxygen-sensitive.

When stock strains of Bacteroides species were held for some hours on swabs, some progressive loss of viability was demonstrable. A measure of protection was afforded when these organisms were held aerobically on blood agar medium, but a very exacting anaerobe and some wild strains of faecal anaerobes showed gradual inactivation under these conditions.

These findings may have important implications in relation to currently employed bacteriological sampling procedures with swabs in clinical practice.

The purpose of this work was to study the effects of interrupted, continuous and post-salmonella inoculation treatment with furazolidone in the feed on the colon-ization of Salmonella infantis in the intestines of chickens, as well as the influence of furazolidone in vitro on the effect of a mixed culture used for the prevention of salmonellosis in chickens.

It was shown that chickens given interrupted treatment with 0·01% furazoli-done had significantly more salmonellas in the caeca than either chickens fed continuously with this drug or chickens without any treatment. The use of 0·01% furazolidone after inoculation with Salmonella infantis had no effect on Salmonella infantis in the caeca of chickens.

The mixed bacterial culture from the normal intestinal flora lost its preventive effect on salmonellosis when cultured with 0·01% furazolidone.

A series of meatal swabs, taken from 17 men over a period of 17 months during their tour at an Antarctic base was examined for mycoplasmas. The number of organisms isolated never exceeded 104 and not every specimen from each man yielded mycoplasmas. Nevertheless, Mycoplasma hominis was isolated from 71% and T-mycoplasmas from 59% of the men at some time during their stay. M. hominis persisted in the presence of serum IHA antibody titres of 1/64. Three subjects yielded only M. hominis and one only T-mycoplasmas.

Six men had already spent a year at the base when the study began and myco-plasmas were still being isolated from some of them at the end of a 31 month period of isolation. The persistence of mycoplasmas in the male genital tract can therefore be independent of sexual contact. Two modes of persistence are suggested; either a few men act as carriers and reinfect the others by contaminating their environment, or as seems more likely, most men have chronic infections.

In the examination of bovine fetal material it was found that there was a significant increase in the proportion of mixed infections identified as the time between abortion and the collection of the samples increased. Examination of paired serum samples from abortions from which only Corynebacterium pyogenes was isolated revealed evidence of active infection in two-thirds, suggesting that C. pyogenes may have been acting as a primary abortifacient in these cases.

With the use of streptomycin-resistant mutants to facilitate recovery, 5 strains of 4 species of Salmonella were shown to grow rapidly at 22° C. on low salt ham even from an inoculum of 10–20 organisms. S. pullorum did not grow well. All 6 strains of Salmonella survived but did not grow on ‘high salt ham’. We conclude that cooked ham containing approximately 2·8 g. NaCl/100 g. H2O once infected is more likely to give rise to food poisoning than is ham with the higher salt content traditionally used.

It has been shown that it is possible to investigate the colonization resistance in individual mice by determining the concentration of a certain contaminant (S.R.-E. coli) in the faeces during the first 4 days after contamination. Experimental contamination is contra-indicated in many cases such as in individuals with decreased resistance to infection. Particularly in this group, the value of the colonization resistance should be determined. It appeared to be possible to determine the colonization resistance in such individuals by quantitative biotyping of the Enterobacteriaceae species in the faeces on several consecutive days.

Of 60 TRIC agents isolated from Gambian children with trachoma, 25 were serotype 1 and the remainder type 2. There was a pronounced difference in the proportions of these types in the two villages studied. In the village with a predominance of type 2 strains, TRIC agents remained confined to 2 adjacent compounds over a 14 month observation period. All 19 type 1 strains examined were characterized by the appearance in yolk sac smears of compact aggregates of elementary bodies; such aggregates were seen in only 2 of 35 type 2 strains, and may reflect a chemical difference in the surface of the elementary bodies or in a substance elaborated during their replication.

An examination was made of the relations between antigen, antibody and fixation of complement with foot-and-mouth disease virus (FMDV). It was found that complement fixation in this system follows the same principles as models developed in other antigen/antibody systems. The assumption that there is a relation of direct proportionality between the amount of complement fixed and the amount of antiserum reacting with constant antigen was found to be incorrect. An alternative method was proposed for the quantitative differentiation of FMDV strains by comparing the titres of an antiserum when reacting with optimum amounts of homologous or heterologous antigens.

Several foot-and-mouth disease virus strains were examined by complement-fixation tests in microplates and in tubes. It was established that the two systems are comparable, although greater reproducibility is obtained with tube tests. While microplate tests are a satisfactory method for the differentiation of strains, tube tests provide a more precise method for the identification of small antigenic differences.

The influence of obstructions and thermals on the air flow in unidirectional or laminar flow systems was studied with special reference to operating rooms. It was shown that thermals induced in the operating rooms would have little influence in the normal laminar-flow system. The importance however of obstructions such as operating lamps and personnel was shown.

Influenza-like illness, cold and sore throat was the diagnosis given in over 80% of 5177 acute respiratory illnesses in patients swabbed over a 10-year-period. A pathogenic organism was isolated twice as frequently from patients with a sore throat or an influenza-like illness as from those diagnosed as suffering from croup or laryngitis and bronchitis. A laboratory diagnosis was commoner in school children than in older or younger persons.

Most of the organisms isolated were found in association with all types of acute respiratory illness but, with increasing age of the patient, one particular agent or group of agents was more likely to be of aetiological significance.

Antibodies neutralizing adenovirus type 5 were found in all of 50 pairs (100%) of sera from patients with acute icteric infectious hepatitis. The incidence in sera from the general population was 57%. No differences in mean titre or in proportion of positive sera were found in the same sera tested for complement-fixing antibodies to cytomegalovirus and for antibodies to rubella virus haemagglutinin. The results can be interpreted as supporting the involvement, either direct or indirect, of adenovirus in the aetiology of infectious hepatitis; but could also be due to a non-specific anamnestic enhancement of the production of antibody to adenovirus, or to coincidental infection with adenovirus and the agent of infectious hepatitis.

An outbreak of cholera occurred in November 1972 among passengers on an aircraft that had flown from London to Sydney. The infection was confined to economy-class passengers and the available evidence indicates that it was due to a dish of hors d'œuvres served on the aircraft between Bahrain and Singapore. Although one person died, the infection was generally mild, and almost half of those infected were symptomless. There was a significant difference between the immunization status of persons with clinical illness and the immunization status of other passengers. Current cholera immunization appeared to play a significant role in preventing symptoms of the disease, but it did not prevent a person becoming a carrier of the organism.

Rabbit fleas for use in Myxomatosis investigations have been successfully bred on rabbits in an animal house. The timing of emergence appeared to be governed by a biological timing control interacting with different forms of disturbance. Yield was found to be related to litter size, the time the doe and her kittens were removed from the nest, the number of fleas put onto a doe before littering and the mean ambient temperature to which the doe was exposed in the week pre-partum. The survival rate of fleas in storage was affected by temperature, the degree of crowding, moisture content of the containers, whether fleas were fed or unfed and the source of fleas in terms of emergence times.

A method of freeze-drying is described by which the activity of a series of corynebacteriophages was maintained over a test period of 30 months, whereas some of these strains became inactive if stored as liquid filtered lysates at 4° C, or frozen and held at − 25° C.

The routine methods used in the Enteric Reference Laboratory for the study of enterobacterial plasmids are described. The results of their application to plasmids of diverse origin, and their value for the categorization of those plasmids, are presented and discussed.